This invention relates to emergency evacuation equipment for aircraft, in particular, to inflatable aircraft evacuation slides.
The requirement for reliably evacuating airline passengers in the event of an emergency is well-known. Emergencies at take-off and landing often demand swift removal of the passengers from the aircraft because of potential for injuries from fire, explosion, and/or sinking in water. A conventional method of quickly evacuating a large number of passengers from an aircraft is to provide multiple emergency exits, each of which is equipped with an inflatable evacuation slide. Emergency evacuation slides must deploy reliably and remain in position notwithstanding the presence of severe crosswinds which tend to twist the slide and/or move the foot end of the slide out of position, rendering the slide unusable.
Various methods and apparatus have been proposed for improving the stability of inflatable evacuation slides during and after deployment when subjected to severe crosswinds. U.S. Pat. No. 5,820,773 to Hintzman, et al. teaches use of a support tube that prevents the evacuation slide from being blown underneath the aircraft during deployment. U.S. Pat. No. 5,102,070 to Smialowicz, et al. teaches use of an inflatable structure that extends into the slide enclosure to provide a rigid mount to help prevent the head end of the slide from twisting out of position. U.S. Pat. No. 3,811,534 to Fisher teaches an oil platform evacuation slide that uses a plurality of guy straps extending at angles outward from the foot end of the inflatable escape slide to head end attachments that are spaced apart substantially wider than the head end of the slide. The guy straps create a trapezoid truss arrangement, which provides for substantial resistance against deformation of the slide under windloads. Use of external guy straps to create a truss for securing the evacuation slide against lateral deformation under wind loads is very effective for evacuation slides for use with oil platforms and the like where the exposed guy straps are mounted to a stationary structure. Use of external guy straps on an aircraft evacuation slide, however, would be disfavored by most aircraft manufactures because of the need to provide concealed mounting points outside of the evacuation slide packboard enclosure. According, what is needed is an aircraft evacuation slide having the lateral stability inherent in a trapezoidal truss, without the need for externally mounted guy stays.
The present invention satisfies the foregoing need by providing an inflatable evacuation slide the main support tubes of which form a trapezoidal truss-like structure. According to one embodiment of the present invention the inflatable evacuation slide comprises a pair of main support tubes supporting a flexible sliding surface. The main support tubes taper from a widest point near the exit opening of the aircraft to a narrowest point at the foot end of the slide. This arrangement of main support tubes, together with the toe end transverse tube and the head end transverse tube, form a quasi-trapezoidal truss structure, which is inherently more stable than the rectangular slides of the prior art. The escape slide may extend normally outward from the aircraft fuselage such that the head end transverse tube and the toe end transverse tube are parallel, in which case the escape slide is a true trapezoid. Alternatively, the escape slide may extend out at an angle from the aircraft fuselage, in which case the head end tube and the toe end tube are not parallel and one of the main support tubes is longer than the other. In the latter case the escape slide is not a true trapezoid but is an irregular quadrilateral (or as used herein, a quasi-trapezoid). In either case, the non-parallel main support tubes that taper towards each other as they extend outward from the aircraft provide a highly stable structure not found in prior art rectangular evacuation slides.